This application proposes to study the interactions of the 4.5S, 5.5S and 7S progesterone receptor complexes, and a postulated non-steroid binding subunit. These macromolecules will be characterized by gel filtration and affinity chromatography. When the subunits are well characterized, we plan to study the induction of specific proteins, such as blastokinin, in the rabbit and guinea pig uterus. We plan to identify the protein by electrophoretic techniques and ascertain which portion of the S7 complex is responsible for its induction. These studies should provide insight into the role of progesterone receptors in reproductive processes.